Funny you should bring this up. I'm in the process of reading both "We Were Soldiers Once and Young" by Col. Hal Moore, and "Street Without Joy" by Bernard Fall. Since I'm reading both, its taking me a bit longer to get through them, but from what I've gathered so far, an incursion into North Vietnam wouldn't have settled anything. Communist forces would've retreated into Cambodia, Laos, and China, resupplied, then re-engaged in their war for liberty. To really understand the underpinnings of America's involvement in Vietnam, you have to understand the events of French occupation prior to WW2, and the Japanese occupationg during WW2, and the French Indochina wars after WW2.
LBJ's big failing was that he thought he could fight the war "on the cheap" by not declaring a state of national emergency that would've allowed him to commit more forces, retain skilled servicemen for longer periods, and used nuclear weapons. The fact that LBJ wasn't willing to go all the way pretty much set the stage for failure, particularly since he had grossly underestimated the determination of the enemy.
The VC weren't the cause of the downfall of South Vietnam, but they contributed. The Meikong Delta just got the most press because it was the hotbed of jungle warfare, booby traps, and political activity.
Col. Moore makes an interesting observation. He knew early on that whomever controlled the Central Highlands would control Vietnam. He "won" the battle at the Ia Drang Valley and set the American presence in the Central Highlands, but that just stalled the eventual collapse for 11 years. He knew that without the resources to hold that valley, it was just a matter of time before the country fell.
You have to remember, the Vietnamese weren't just fighting for Communism, they were fighting for their independence as a unified nation. They just happened to be led by Communists because America dropped the ball in WW2 by failing to support French forces fighting there against the Japanese. When the Japanese pulled out, the Communist movement worked to fill the void and be the central political voice there when Japan surrendered. If the French had held out, and if the US had provided support, and if Chennault had been permitted to provide overt support from Nationalist China (he disobeyed orders and provided covert support, which led to his removal from command), the situation would've been much different. France was awarded Vietnam as a colony after WW2 for two key reasons (a) as compensation for its role as an Allied nation and (b) because the US figured France could keep the Communist Menace at bay during the Cold War. Had the US assisted the French troops fighting the Japanese in Indochina, the move for independence might have been in the form of a democratic republic rather than Communist leadership.
Tell that to your high school History teacher and see if his eyes bug out.
